Chinese stock markets tumbled again on Monday as it emerged that the Beijing authorities spent nearly $100bn last month propping up the yuan.

The $94bn (£61bn) fall in central bank reserves was the biggest on record, although in percentage terms it was the biggest for three years.

Investors in China returning to their trading desks after a long weekend reacted to falls in stocks in the US and Europe on Friday. The sell-off pushed the Shanghai and Shenzhen CSI 300 index down by 3.4%, leaving the wider Shanghai composite index down by 2.5%.

It came despite the country’s central bank governor, Zhou Xiaochuan, trying to calm nerves, arguing that the “correction in the stock market is almost done”. He predicted markets would be more stable after weeks of turbulence.

His message was reinforced by China’s top economic planning agency, which declared that the economy’s growth prospects were improving. The NDRC said: “The power usage, rail freight, as well as real estate prices and turnover have all improved into August, indicating the economy is stabilising amid fluctuations.”

Beijing also received a show of international support over the weekend. G20 finance ministers and central bankers said they backed last month’s yuan devaluation, as part of the difficult journey to a more market-determined exchange rate.

China suddenly depreciated the value of the yuan against the dollar last month after a surprise fall in exports in July. Investors around the world panicked at the move which triggered weeks of turmoil on global markets.

To prevent the yuan falling too far Beijing more than doubled the funds it used to support the currency during August to $93.9bn.

At $3.56tn, the currency reserves held by the People’s Bank of China are still substantial and account for nearly a third of all holdings by central banks worldwide. But the recent spending has helped push down the value of its reserves from a peak of nearly $4tn in June 2014.

Chris Weston, an analyst at the spread betting firm IG, said stock market traders were likely to take heart over the coming days from the support offered by the central bank.

“Whether or not we have realistically seen the lows in the various Chinese markets is yet to be seen, but the belief and assurance provided by the Chinese authorities over the weekend suggests we may see better days ahead,” he said. “Of course, one day doesn’t make a bull market. However, when you hear that power usage, train freight and property markets are showing signs of improvement, domestic traders listen.”

The Shanghai stock market is dominated by day traders, in contrast to markets in London, New York and continental Europe which are influenced by institutional investors.

Beijing has recently allowed public sector pension funds to invest in domestic company shares, but too late to prevent wild gyrations in values that forced it to inject vast sums to prevent a collapse.